An LTE system is an OFDMA-based communication system designed to support Frequency Division Duplex (FDD) and Time Division Duplex (TDD). Also, it is designed to support half duplex transmission. The LTE system has been designed for the goal of supporting FDD and TTD on a single carrier in Release 8 and then FDD and TDD on one or more carriers in Release 10 under the assumption that the uplink and downlink transmission directions of the carriers are identical each other in TDD. In addition to those features, Release 11 aims to support the TDD system having the carriers with uplink and downlink transmission directions different in time from each other and the design thereon is under progress.
Meanwhile, it may occur that a plurality of carriers having different TDD configurations are aggregated such that a special subframe and a downlink subframe are scheduled simultaneously at the same subframe duration and thus the uplink part of the special subframe and the downlink subframe conflict each other. This is likely to cause a problem to the terminal operating in the half duplex-duplex mode which cannot transmit and receive at the same time.
In the case of Physical Random Access Channel (PRACH) transmitted in the uplink part of the special subframe, its transmission timing is determined by the terminal and not changed by the base station's scheduling and, if the downlink transmission is suspended at the downlink subframe to guarantee the uplink transmission at the special subframe, this may cause a problem of wasting the frequency resource even when the terminal operates in reception mode at the downlink part of the special subframe.